CN112061227B

CN112061227B - Steer-by-wire system for vehicle and method of controlling the same

Info

Publication number: CN112061227B
Application number: CN202010518840.2A
Authority: CN
Inventors: 金泰弘
Original assignee: Hyundai Mobis Co Ltd
Current assignee: Hyundai Mobis Co Ltd
Priority date: 2019-06-11
Filing date: 2020-06-09
Publication date: 2023-05-23
Anticipated expiration: 2040-06-09
Also published as: US11618497B2; KR20200141728A; US20200391789A1; KR102646187B1; CN112061227A

Abstract

The present disclosure relates to a steer-by-wire system for a vehicle, which may include: a reaction motor that provides a reaction torque based on rotation of the steering wheel; a steering motor that performs steering operation; a motor position detector that measures a current steering angle by detecting a rotational position of the steering motor; a position controller calculating a target steering angle by applying a position control error amount to a vehicle speed, a command steering angle, and a current steering angle; a steering controller that drives a steering motor based on a target steering angle; and a reaction controller that generates reaction torque based on a steering state of the driver by receiving the vehicle speed and the steering angular velocity; compensating for the reaction torque based on the amount of position control error; and driving the reaction motor based on the final reaction torque.

Description

Steer-by-wire system for vehicle and method of controlling the same

Cross Reference to Related Applications

The present application claims priority and rights of korean patent application No. 10-2019-0068609 filed on date 6 and 11 of 2019, which is incorporated herein by reference for all purposes as if set forth herein.

Technical Field

Exemplary embodiments of the present disclosure relate to a steer-by-wire (SBW) system for a vehicle and a method of controlling the same, and more particularly, to an SBW system for a vehicle, which compensates for a reaction torque based on a position control error amount of a steering motor so that a reaction torque without a difference feeling can be generated and the driver can have a road feeling, when transferring control right based on a steering intention of the driver while automatically driving in the SBW system using the SBW method, wherein the SBW method includes driving the steering motor coupled with a rack to perform a steering operation and generate the reaction torque based on a vehicle speed and a steering angle.

Background

In general, power steering of a vehicle relates to a power steering apparatus based on motor power, and has a function of helping a driver to steer a steering wheel. Basically, a method using oil pressure is used for such power steering. Recently, motor-driven power steering (MDPS) systems, i.e., methods using motor power, are increasingly used. The reason for this is that the MDPS system has advantages of light weight, small occupied space and no need of oil change as compared with the existing oil pressure type power steering system.

Such an MDPS system is configured to include: a torque sensor for generating an electric signal proportional to a steering torque by detecting the steering torque generated by rotation of a steering wheel; an electronic control unit (electronic control unit, ECU) for generating a motor drive signal by receiving an electrical signal from the torque sensor; and a motor for generating an assist torque based on a motor drive signal generated by the ECU. Accordingly, the assist torque generated by the motor is transmitted to the rack, pinion or steering column to assist the steering torque of the driver.

Active front steering (active front steering, AFS) or variable gear ratio (variable gear ratio, VGR) systems may be suitable for vehicles on which MDPS systems have been installed, where the AFS or VGR systems are capable of achieving faster or more accurate steering by altering the ratio of the steering input to the wheel output angle of the driver (i.e., steering gear ratio),

in the AFS system, a steering gear ratio variable device is provided between a steering wheel and a steering actuator. The steering gear ratio variable device changes the steering gear ratio by receiving the steering angle of the steering wheel and outputting the changed rotation angle to the steering actuator. Typically, the AFS system changes the steering gear ratio based on the vehicle speed. Accordingly, the AFS system can obtain a quick steering characteristic by setting a high steering gear ratio at a low speed, and can perform a stable steering operation since the steering sensitivity is reduced by setting a low steering gear ratio at a high speed.

The VGR system changes the steering gear ratio by mechanical processing of the rack for converting rotational movement of the pinion at the end of the steering column into linear movement, and changes the steering gear ratio by changing the displacement of the rack based on the steering angle. In such VGR systems, the steering gear ratio varies depending on the steering angle. Accordingly, the VGR system can obtain better steering characteristics by setting a low steering gear ratio at a small steering angle, and obtain faster steering characteristics by setting a high gear ratio at a large steering angle.

A SBW system has recently been developed and applied in which a mechanical connection means (such as a steering column or a universal joint, and a pinion shaft between a steering wheel and wheels) is removed, and steering of a vehicle is performed by controlling driving of a motor coupled with a rack based on an electric signal. Such an SBW system may be configured to include: steering wheel for driver steering; a reaction motor disposed on one side of the steering wheel to provide reaction torque based on rotation of the steering wheel; a steering motor coupled to the rack to perform a steering maneuver; a sensor for detecting a steering angle; vehicle speed and steering wheel torque; and an ECU for driving the steering motor and the reaction motor in response to the electric signals received from the sensor.

An advantage of such SBW systems is that, because there is no mechanical connection, damage to the driver caused by mechanical components can be reduced when the vehicle collides; the weight of the vehicle can be reduced by reducing the mechanical connection parts; unnecessary energy consumption in steering operation can be reduced, and desired steering performance can be achieved by ECU programming. Thus, the use of SBW systems tends to increase gradually.

The related art of the present disclosure is disclosed in korean patent application publication No. 10-2018-0007393 (month 23 of 2018, entitled "apparatus for controlling steering in steer-by-wire system and method thereof").

Disclosure of Invention

However, in such SBW systems, it is impossible for the driver to have a road feel physically transferred to the steering wheel through the wheels of the vehicle, because the reaction force control and the steering control are performed by electric wires in a state where the mechanical connection parts have been removed.

Therefore, the SBW system may give a heavy feeling to the driver when steering is performed by the reaction control, but there is a problem in that it cannot provide a steering feeling based on the road surface or the behavior of the vehicle, and thus inevitably provides a somewhat artificial steering feeling rather than a natural steering feeling.

Further, in an autonomous vehicle to which the SBW system has been applied, in the autonomous mode, since the wheels of the vehicle and the steering wheel are not physically coupled, reaction control is not performed on the steering wheel. However, the autonomous vehicle has the following problems: in the automatic driving mode, when the control right is transferred to the driver due to the release of the automatic driving mode caused by the steering of the driver, if the reaction control is suddenly performed, a sense of difference in steering occurs and the immediate control stability is lowered.

Various embodiments are directed to providing an SBW system for a vehicle and a method of controlling the same, which compensates a reaction torque based on a position control error amount of a steering motor when transferring control right based on a steering intention of a driver while automatically driving in the SBW system using an SBW method, so that a reaction torque without a sense of difference can be generated and the driver can have a road feel, wherein the SBW method includes driving the steering motor coupled with a rack to perform a steering operation and generate the reaction torque based on a vehicle speed and a steering angle.

In one embodiment, a steer-by-wire (SBW) system for a vehicle includes: a reaction motor located on one side of the steering wheel and configured to generate a reaction torque based on rotation of the steering wheel; a steering motor coupled to the rack and configured to perform a steering maneuver; a motor position detector configured to measure a current steering angle by detecting a rotational position of the steering motor; a position controller configured to receive a vehicle speed, a commanded steering angle, and the current steering angle, and calculate a target steering angle by applying a position control error amount to the position controller; a steering controller configured to drive the steering motor based on the target steering angle output by the position controller; and a reaction controller configured to generate the reaction torque based on a steering state of the driver by receiving a vehicle speed and a steering angular velocity; compensating for the reaction torque based on the amount of position control error; and driving the reaction motor based on the final reaction torque.

In one embodiment, the reaction controller includes: a reaction torque generator configured to generate the reaction torque based on the vehicle speed and the steering angular velocity; a variable filter unit configured to filter out the position control error amount by changing a cutoff frequency of a low-frequency filter based on the vehicle speed and the steering angular velocity; and a reaction compensator configured to compensate the reaction torque based on the position control error amount filtered out by the variable filter unit, and output the final reaction torque.

In one embodiment, the variable filter unit is configured to set the cutoff frequency of the low-frequency filter to be low when the vehicle speed and the steering angular velocity are high, and to set the cutoff frequency of the low-frequency filter to be high when the vehicle speed and the steering angular velocity are low.

In one embodiment, the variable filter unit is configured to set a cut-off frequency of the low-frequency filter based on a two-dimensional map (two-dimensional map) using the vehicle speed and the steering angular velocity.

In one embodiment, the reaction controller includes: a reaction torque generator configured to generate the reaction torque based on the vehicle speed, the steering angular velocity, and the position control error amount; a steering mode determination unit configured to determine a driver steering mode based on the position control error amount; a weight setting unit configured to set a mode change weight based on a result determined by the steering mode determining unit; and an output unit configured to output the final reaction torque by applying the mode change weight set by the weight setting unit to the reaction torque.

In one embodiment, the steering mode determining unit is configured to determine that the steering mode is the driver steering mode when the position control error amount is maintained at a set value or more for a set time or more.

In one embodiment, the weight setting unit is configured to set a maximum mode change weight in an automatic driving mode and a minimum mode change weight in the driver steering mode.

In one embodiment, the weight setting unit is configured to: if a steering mode is determined as the driver steering mode, the slope of the mode change weight is changed and set based on the position control error amount or the steering angular velocity.

In one embodiment, the reaction controller includes: a reaction torque generator configured to generate the reaction torque based on the vehicle speed and the steering angular velocity; a variable filter unit configured to filter out the position control error amount by changing a cutoff frequency of a low-frequency filter based on the vehicle speed and the steering angular velocity; a reaction compensator configured to compensate the reaction torque based on the position control error amount filtered out by the variable filter unit; a steering mode determination unit configured to determine a driver steering mode based on the position control error amount; a weight setting unit configured to set a mode change weight based on a result determined by the steering mode determining unit; and an output unit configured to output the final reaction torque by applying the mode change weight set by the weight setting unit to the reaction torque.

In one embodiment, a method of controlling a steer-by-wire (SBW) system for a vehicle includes: receiving, by a position controller, a vehicle speed, a commanded steering angle, and a current steering angle, and calculating a target steering angle by applying a position control error amount to the position controller; driving, by a steering controller, a steering motor based on the target steering angle; generating, by the reaction controller, a reaction torque based on a steering state of the driver by receiving the vehicle speed and the steering angular velocity; and driving, by the reaction controller, a reaction motor based on a final reaction torque, wherein the final reaction torque is obtained by compensating the generated reaction torque based on the position control error amount.

In one embodiment, the drive reaction motor comprises: filtering, by the reaction controller, the amount of position control error by changing a cutoff frequency of a low-frequency filter based on the vehicle speed and the steering angular velocity; and compensating, by the reaction controller, the reaction torque based on the filtered position control error amount, and driving the reaction motor.

In one embodiment, the cutoff frequency of the low frequency filter is set to be low when the vehicle speed and the steering angular velocity are high, and the cutoff frequency of the low frequency filter is set to be high when the vehicle speed and the steering angular velocity are low.

In one embodiment, the cutoff frequency of the low frequency filter is set based on a two-dimensional map using the vehicle speed and the steering angular velocity.

In one embodiment, the drive reaction motor comprises: determining, by the reaction controller, a driver steering mode based on the amount of position control error; setting, by the reaction controller, a mode change weight based on a determination result of the driver steering mode; and driving, by the reaction controller, the reaction motor based on the final reaction torque by applying a set mode change weight to the reaction torque.

In one embodiment, the determining the driver steering mode includes: when the position control error amount is maintained at a set value or more for a set time or more, a steering mode is determined as the driver steering mode by the reaction controller.

In one embodiment, the setting the mode change weight includes: setting, by the reaction controller, a maximum mode change weight in an autopilot mode; and setting, by the reaction controller, a minimum mode change weight in the driver steering mode.

In one embodiment, the setting the mode change weight includes: when a steering mode is determined as the driver steering mode, the slope of the mode change weight is changed and set by the reaction controller based on the position control error amount or the steering angular velocity.

Drawings

FIG. 1 illustrates a block diagram of a steer-by-wire (SBW) system for a vehicle according to an embodiment of the present disclosure.

FIG. 2 illustrates a block diagram of a reaction controller for an SBW system of a vehicle, according to an embodiment of the present disclosure.

FIG. 3 illustrates a block diagram of a reaction controller for an SBW system of a vehicle, according to another embodiment of the present disclosure.

FIG. 4 illustrates a block diagram of a reaction controller for an SBW system of a vehicle, according to another embodiment of the present disclosure.

FIG. 5 illustrates a flowchart of a method of controlling an SBW system for a vehicle, according to an embodiment of the present disclosure.

FIG. 6 illustrates a flowchart of a method of controlling an SBW system for a vehicle, according to another embodiment of the present disclosure.

Detailed Description

Hereinafter, a steer-by-wire (SBW) system for a vehicle and a method of controlling the same will be described with reference to the accompanying drawings by various exemplary embodiments. The figures are not to precise scale and the widths of the lines or the dimensions of the elements may be exaggerated for convenience and clarity of illustration only. Further, the terms used herein are defined by considering the functions of the present disclosure, and may be changed according to the habit or intention of a user or operator. The definition of terms is therefore defined in accordance with the entire disclosure herein.

Fig. 1 shows a block diagram of a steer-by-wire (SBW) system for a vehicle according to an embodiment of the present disclosure, and fig. 2 shows a block diagram of a reaction controller of an SBW system for a vehicle according to an embodiment of the present disclosure.

As shown in fig. 1, an SBW system for a vehicle according to an embodiment of the present disclosure may include: reaction motor 60, steering motor 30, motor position detector 40, position controller 10, steering controller 20, and reaction controller 50.

The reaction motor 60 may be located on one side of the steering wheel (not shown) and may generate reaction torque based on the rotation of the steering wheel.

The steering motor 30 may be coupled to a rack (not shown), and may perform a steering operation by rotating the wheels in a desired direction by moving the rack.

The motor position detector 40 may provide a current steering angle, which is measured by detecting the rotational position of the steering motor, so that feedback control may be performed by recognizing the road surface state at the time of position control.

The position controller 10 may receive the vehicle speed, the commanded steering angle, and the current steering angle, and may calculate the target steering angle by applying the position control error amount to the position controller.

In this case, when the driver manipulates the steering wheel in the driver steering mode, the command steering angle may be a steering angle based on the rotation of the steering wheel, and may also be a steering angle output by an automatic driving controller (not shown) in the automatic driving mode.

Further, if the driver steers the steering wheel in such a state (the friction force of the road surface is high, there is an obstacle, or the self-alignment force is large in the case where the vehicle speed is present), or the driver steers the steering wheel in the case where the lateral force is generated due to wind, the amount of position control error is higher than in the normal state.

The steering controller 20 drives the steering motor 30 based on a target steering angle, which is output by the position controller 10 through feedback control, to thereby perform steering.

The reaction controller 50 may generate the reaction torque based on the steering state of the driver by receiving the vehicle speed and the steering angular velocity; compensating for the reaction torque based on the amount of position control error; and driving the reaction motor 60 based on the final reaction torque so that the driver can have a steering feel.

In this case, as shown in fig. 2, the reaction controller 50 may include: a reactive torque generator 510, a variable filter unit 512, and a reactive compensator 514.

The reaction torque generator 510 may calculate a rack force according to a vehicle model based on a vehicle speed and a steering angular velocity, and may generate a reaction torque.

The variable filter unit 512 may filter out the amount of position control error by changing the cutoff frequency of the low-frequency filter based on the vehicle speed and the steering angular velocity.

If the position control error amount that varies according to the load condition of the road surface is applied to the reaction torque without any change, the driver may feel a sense of difference. Accordingly, the variable filter unit 512 may change the cut-off frequency of the low frequency filter based on the vehicle speed and the steering angular velocity so that the driver may have a natural steering feel.

For example, when the vehicle speed and the steering angular velocity are high, the variable filter unit 512 may lower the cut-off frequency of the low-frequency filter so as to remove the vibration component of the high-frequency component. In contrast, when the vehicle speed and the steering angular velocity are low, the variable filter unit 512 may raise the cut-off frequency of the low-frequency filter so that the driver has a natural steering feel while having a maximum road feel or external force feel.

In the present embodiment, the variable filter unit 512 may set the cut-off frequency of the low-frequency filter so that the driver can have a natural steering feel through tuning using a two-dimensional map based on the vehicle speed and the steering angular velocity.

The reaction compensator 514 may compensate the reaction torque based on the position control error amount filtered out by the variable filter unit 512, and may output a final reaction torque.

In this case, the reaction compensator 514 may set the amount of reaction current to be compensated by tuning so that the driver may have a natural road feel based on the filtered position control error amount, and may output the final reaction torque by incorporating the set amount of reaction current into the reaction torque.

As shown in fig. 3, the reaction controller 50 of the SBW system for a vehicle may include: a reaction torque generator 520, a steering mode determination unit 522, a weight setting unit 524, and an output unit 526.

The reaction torque generator 520 may generate reaction torque, whereby the driver may have a steering feel when turning the steering wheel based on the vehicle speed, the steering angular velocity, and the position control error amount.

The steering mode determination unit 522 may determine the driver steering mode based on the position control error amount calculated in the position controller 10 based on the commanded steering angle and the current steering angle to feedback-control the steering motor 30.

In this case, the steering mode determination unit 522 may determine that the steering mode is the driver steering mode when the position control error amount is maintained at the set value or more for the set time or more.

For example, in general, in the automatic driving mode, since the driver does not manipulate the steering wheel, the amount of position control error is concentrated on a small value. However, if a lateral force is applied to the vehicle due to the state of the road surface or the surrounding environment, a given amount of position control error may occur even in the automatic driving mode. Further, even when the vehicle runs on a road surface or a foreign matter such as a stone in a pothole, the amount of position control error may occur instantaneously at a given level.

Therefore, when the position control error amount is not maintained for the set time or longer, the steering mode determination unit 522 may determine that the temporary change as described above is due to the surrounding environment, and determine that the steering mode is the automatic driving mode. The steering mode determination unit 522 may determine that the driver has a steering intention and determine that the steering mode is the driver steering mode only when the position control error amount remains at the set value or more for the set time or more.

The weight setting unit 524 may set the mode change weight based on the result determined by the steering mode determining unit 522.

In this case, the weight setting unit 524 may set the maximum mode change weight in the automatic driving mode and may set the minimum mode change weight in the driver steering mode.

That is, the weight setting unit 524 may set the mode change weight such that the reaction torque is not output in the autonomous driving mode and the generated reaction torque is output to the maximum value in the driver steering mode.

Further, if the steering mode is determined to be the driver steering mode, the weight setting unit 524 may change and set the slope of the mode change weight based on the position control error amount or the steering angular velocity so that the driver does not feel a sense of difference when the control right is transferred from the automatic driving mode to the driver steering mode. For this reason, the weight setting unit 524 may increase the slope of the mode change weight when the amount of position control error is large by abrupt steering, and the weight setting unit 524 may decrease the slope of the mode change weight when the amount of position control error is small by slow steering.

The output unit 526 may output the final reaction torque by applying the mode change weight set by the weight setting unit 524 to the reaction torque.

For example, the output unit 526 may output the final reaction torque by multiplying (1-mode change weight) and the reaction torque.

Therefore, the output unit 526 does not output the reaction torque because the mode change weight is "1" in the automatic driving mode, and the output unit 526 may output the reaction torque because the mode change weight is "0" in the driver steering mode.

FIG. 4 shows a block diagram of a reaction controller 50 for an SBW system of a vehicle according to another embodiment of the present disclosure.

As shown in fig. 4, the reaction controller 50 of the SBW system for a vehicle may include: a reaction torque generator 510, a variable filter unit 512, a reaction compensator 514, a steering mode determination unit 522, a weight setting unit 524, and an output unit 526.

The reaction controller shown in fig. 4 is a combination of the reaction controllers shown in fig. 2 and 3, and a detailed description thereof is omitted.

The reaction torque generator 510 may generate reaction torque by calculating rack force according to a vehicle model based on a vehicle speed and a steering angular velocity.

The reaction compensator 514 may compensate the reaction torque based on the amount of position control error filtered by the variable filter unit 512.

In this case, the reaction compensator 514 may set the amount of reaction current to be compensated by tuning so that the driver may have a natural road feel based on the filtered position control error amount, and may compensate the reaction torque by incorporating the set amount of reaction current into the reaction torque.

The steering mode determination unit 522 may determine the driver steering mode based on the position control error amount calculated in the position controller 10 based on the commanded steering angle and the current steering angle meter to feedback-control the steering motor 30.

In this case, the weight setting unit 524 may set the maximum mode change weight in the automatic driving mode and the minimum mode change weight in the driver steering mode.

As described above, according to the SBW system for a vehicle according to an embodiment of the present disclosure, in the SBW system using the SBW method that includes driving a steering motor coupled with a rack to perform a steering operation and generate a reaction torque based on a vehicle speed and a steering angle, when a control right is transferred based on a steering intention of a driver at the time of automatic driving, a weight is set based on a position control error amount and the reaction torque is compensated. Therefore, since the difference feeling is eliminated and the reaction torque is compensated based on the position control error amount of the steering motor, the driver can have the road feeling.

As shown in fig. 5, in a method of controlling an SBW system for a vehicle according to an embodiment of the present disclosure, first, at step S10, the position controller 10 receives a vehicle speed, a commanded steering angle, and a current steering angle, and calculates a target steering angle by applying a position control error amount to the position controller.

In step S20, the steering controller 50 drives the steering motor 30 based on the target steering angle, which is output by the position controller 10 through the feedback control in step S10, to thereby perform steering.

In step S30, the reaction controller 50 generates a reaction torque based on the steering state of the driver by calculating a rack force according to the vehicle model based on the vehicle speed and the steering angular velocity.

After generating the reaction torque at step S30, the reaction controller 50 filters out the amount of position control error by changing the cutoff frequency of the low-frequency filter based on the vehicle speed and the steering angular velocity at step S40.

If the position control error amount that varies according to the load condition of the road surface is applied to the reaction torque without any change, the driver may feel a sense of difference. Accordingly, the reaction controller 50 may change the cutoff frequency of the low frequency filter based on the vehicle speed and the steering angular velocity so that the driver may have a natural steering feel.

For example, when the vehicle speed and the steering angular velocity are high, the reaction controller 50 may decrease the cutoff frequency of the low-frequency filter so as to remove the vibration component of the high-frequency component. Conversely, when the vehicle speed and the steering angular velocity are low, the reaction controller 50 may raise the cutoff frequency of the low frequency filter so that the driver has a natural steering feel while having a maximum road surface feel or external force feel.

In the present embodiment, the reaction controller 50 may set the cutoff frequency of the low-frequency filter so that the driver can have a natural steering feel through tuning using a two-dimensional map based on the vehicle speed and the steering angular velocity.

After filtering out the position control error amount based on the vehicle speed and the steering angular velocity at step S40, the reaction controller 50 compensates the reaction torque based on the filtered out position control error amount at step S50.

In this case, the reaction controller 50 can set the amount of reaction current to be compensated by tuning so that the driver can have a natural road feel based on the filtered position control error amount, and can output the final reaction torque by incorporating the set amount of reaction current into the reaction torque.

In step S50, the reaction controller 50 drives the reaction motor 60 based on the final reaction torque obtained by compensating the reaction torque in step S50, so that the driver can have a natural road feel.

As shown in fig. 6, in a method of controlling an SBW system for a vehicle according to another embodiment, step S100, first, the position controller 10 receives a vehicle speed, a commanded steering angle, and a current steering angle, and calculates a target steering angle by applying a position control error amount to the position controller.

In step S110, the steering controller 20 drives the steering motor 30 based on the target steering angle, which is output by the position controller 10 through the feedback control in step S110, to thereby perform steering.

In step S120, the reaction controller 50 generates a reaction torque based on the steering state of the driver based on the vehicle speed, the steering angular velocity, and the position control error amount.

After generating the reaction torque at step S120, the reaction controller 50 determines the driver steering mode based on the position control error amount calculated in the position controller 10 based on the commanded steering angle and the current steering angle to feedback-control the steering motor 30 at step S130.

In this case, when the position control error amount is maintained at the set value or more for the set time or more, the reaction controller 50 may determine that the steering mode is the driver steering mode.

For example, in general, in the automatic driving mode, since the driver does not manipulate the steering wheel, the amount of position control error is concentrated on a small value. However, if a lateral force is applied to the vehicle due to the state of the road surface or the surrounding environment, a given amount of position control error may occur even in the automatic driving mode. Further, even when the vehicle runs on a road surface or a foreign matter such as a stone in a depression, the amount of position control error may occur instantaneously at a given level, and rebound symptoms may occur.

Therefore, when the position control error amount is not maintained for the set time or longer, the steering mode determination unit 522 may determine that the temporary change as described above is due to the surrounding environment, and determine that the steering mode is the automatic driving mode. The steering mode determination unit 522 may determine that the driver has a steering intention and that the steering mode is the driver steering mode only when the position control error amount remains at the set value or more for the set time or more.

After determining the driver steering mode at step S130, the reaction controller 50 sets a mode change weight based on the result of the determination at step S140.

In this case, the reaction controller 50 may set the maximum mode change weight in the automatic driving mode and the minimum mode change weight in the driver steering mode.

That is, the reaction controller 50 may set the mode change weight such that the reaction torque is not output in the autonomous driving mode, and the generated reaction torque is output to the maximum value in the driver steering mode.

Further, if the steering mode is determined to be the driver steering mode, the reaction controller 50 may change and set the slope of the mode change weight based on the position control error amount or the steering angular velocity so that the driver does not feel a sense of difference when the control right is transferred from the automatic driving mode to the driver steering mode. For this reason, the reaction controller 50 may increase the slope of the mode change weight when the amount of position control error is large by abrupt steering, and the reaction controller 50 may decrease the slope of the mode change weight when the amount of position control error is small by slow steering.

After the mode change weight is set at step S140, the reaction controller 50 calculates a final reaction torque by applying the set mode change weight to the reaction torque at step S150.

For example, the reaction controller 50 may output the final reaction torque by multiplying the (1-mode change weight) and the reaction torque.

In step S160, the reaction controller 50 drives the reaction motor 60 based on the final reaction torque calculated in step S150.

Thus, since the mode change weight is "1" in the automatic driving mode, the reaction torque may not be output, and since the mode change weight is "0" in the driver steering mode, the reaction torque may be output.

As described above, according to the SBW system for a vehicle and the method of controlling the same according to an aspect of the present disclosure, in the SBW system using the SBW method including driving a steering motor connected to a rack to perform a steering operation and generating a reaction torque based on a vehicle speed and a steering angle, when transferring control rights based on a steering intention of a driver at the time of automatic driving, the weights and compensating the reaction torque are set based on a position control error amount. Therefore, the driver can have a road feel because the difference feel is eliminated and the reaction torque is compensated based on the position control error amount of the steering motor.

Furthermore, the embodiments described in this specification may be implemented in the form of a method or process, an apparatus, a software program, a data stream, or a signal. Although the features discussed in the context are implemented in only a single form (e.g., discussed as a method only), the features discussed may also be implemented in another form (e.g., an apparatus or program). The apparatus may be implemented in suitable hardware, software or firmware form. A method may be implemented in an apparatus, such as a processor generally representing a processing device including a computer, microprocessor, integrated circuit, or programmable logic device. The processor includes communication devices such as computers, cellular telephones, portable/Personal Digital Assistants (PDAs), and other devices that facilitate communication of information between end users.

Although the preferred embodiments of the present disclosure have been disclosed for illustrative purposes, those skilled in the art will appreciate that various modifications, additions and substitutions are possible, without departing from the scope and spirit of the disclosure as disclosed in the accompanying claims.

Claims

1. A steer-by-wire (SBW) system for a vehicle, comprising:

a reaction motor located on one side of the steering wheel and configured to generate a reaction torque based on rotation of the steering wheel;

a steering motor coupled to the rack and configured to perform a steering maneuver;

a motor position detector configured to measure a current steering angle by detecting a rotational position of the steering motor;

a position controller configured to receive a vehicle speed, a commanded steering angle, and the current steering angle of the steering motor, and calculate a target steering angle by applying a position control error amount of the steering motor to the position controller;

a steering controller configured to drive the steering motor based on the target steering angle output by the position controller; and

a reaction controller configured to generate the reaction torque based on a steering state of a driver by receiving a vehicle speed and a steering angular velocity; compensating for the reaction torque based on the amount of position control error; and driving the reaction motor based on the final reaction torque,

The reaction controller includes:

a reaction torque generator configured to generate the reaction torque based on the vehicle speed, the steering angular velocity, and the position control error amount;

a steering mode determination unit configured to determine a driver steering mode based on the position control error amount;

a weight setting unit configured to set a mode change weight based on a result determined by the steering mode determining unit; and

an output unit configured to output the final reaction torque by applying the mode change weight set by the weight setting unit to the reaction torque.

2. The SBW system of claim 1, wherein the reaction controller further comprises:

a variable filter unit configured to filter out the position control error amount by changing a cutoff frequency of a low-frequency filter based on the vehicle speed and the steering angular velocity; and

a reaction compensator configured to compensate the reaction torque based on the position control error amount filtered out by the variable filter unit.

3. The SBW system of claim 2, wherein the variable filter unit is configured to:

Setting a cutoff frequency of the low frequency filter to be low when the vehicle speed and the steering angular velocity are high; and

when the vehicle speed and the steering angular velocity are low, the cutoff frequency of the low frequency filter is set high.

4. The SBW system according to claim 2, wherein the variable filter unit is configured to set a cut-off frequency of the low-frequency filter based on a two-dimensional map using the vehicle speed and the steering angular velocity.

5. The SBW system according to claim 1, wherein the steering mode determining unit is configured to determine that the steering mode is the driver steering mode when the position control error amount is maintained at a set value or more for a set time or more.

6. The SBW system according to claim 1, wherein the weight setting unit is configured to:

setting a maximum mode change weight in the automatic driving mode; and

a minimum mode change weight is set in the driver steering mode.

7. The SBW system according to claim 1, wherein the weight setting unit is configured to: if a steering mode is determined as the driver steering mode, the slope of the mode change weight is changed and set based on the position control error amount or the steering angular velocity.

8. The SBW system of claim 1, wherein the reaction controller includes:

a reaction torque generator configured to generate the reaction torque based on the vehicle speed and the steering angular velocity;

a variable filter unit configured to filter out the position control error amount by changing a cutoff frequency of a low-frequency filter based on the vehicle speed and the steering angular velocity;

a reaction compensator configured to compensate the reaction torque based on the position control error amount filtered out by the variable filter unit;

9. A method of controlling a steer-by-wire (SBW) system for a vehicle, comprising:

receiving, by a position controller, a vehicle speed, a commanded steering angle, and a current steering angle of a steering motor, and calculating a target steering angle by applying a position control error amount of the steering motor to the position controller;

Driving, by a steering controller, a steering motor based on the target steering angle;

generating, by the reaction controller, a reaction torque based on a steering state of the driver by receiving the vehicle speed and the steering angular velocity; and

driving a reaction motor by the reaction controller based on a final reaction torque, wherein the final reaction torque is obtained by compensating the generated reaction torque based on the position control error amount,

the drive reaction motor includes:

determining, by the reaction controller, a driver steering mode based on the amount of position control error;

setting, by the reaction controller, a mode change weight based on a determination result of the driver steering mode; and

the reaction motor is driven based on the final reaction torque by the reaction controller by applying a set mode change weight to the reaction torque.

10. The method of claim 9, wherein the driving a reaction motor further comprises: filtering, by the reaction controller, the amount of position control error by changing a cutoff frequency of a low-frequency filter based on the vehicle speed and the steering angular velocity; and

The reaction torque is compensated by the reaction controller based on the filtered out amount of position control error.

11. The method according to claim 10, wherein when the vehicle speed and the steering angular velocity are high, a cutoff frequency of the low-frequency filter is set low, and when the vehicle speed and the steering angular velocity are low, the cutoff frequency of the low-frequency filter is set high.

12. The method according to claim 10, wherein a cutoff frequency of the low frequency filter is set based on a two-dimensional map using the vehicle speed and the steering angular velocity.

13. The method of claim 9, wherein the determining a driver steering mode comprises: when the position control error amount is maintained at a set value or more for a set time or more, a steering mode is determined as the driver steering mode by the reaction controller.

14. The method of claim 9, wherein the setting a mode change weight comprises:

setting, by the reaction controller, a maximum mode change weight in an autopilot mode; and

a minimum mode change weight is set by the reaction controller in the driver steering mode.

15. The method of claim 9, wherein the setting a mode change weight comprises:

when a steering mode is determined as the driver steering mode, the slope of the mode change weight is changed and set by the reaction controller based on the position control error amount or the steering angular velocity.